Fuzzy dark matter dynamical friction

Stalling of globular clusters induced by dynamical heating

¹ LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS, 92190, Meudon, France
² David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 24 November 2025
Accepted: 5 April 2026

Abstract

We present a new implementation of fuzzy dark matter (FDM) dynamical friction within the galpy framework, enabling orbital integrations of globular clusters (GCs) across a broad range of halo-to-GC mass ratios and boson masses. In this alternative DM scenario, dynamical friction is reduced or even suppressed by heating induced by FDM density granules. We further quantified the role of baryons and solitonic cores, which are natural consequences of FDM in galaxies, on the efficiency of orbital decay and the long-term survival of GCs. The most significant deviations from the cold DM (CDM) paradigm arise in the dwarf-galaxy regime, where FDM dynamical friction can stall the inspiral of GCs over Hubble time, thereby preventing them from sinking into galactic centres and halting the canonical galactic cannibalism of clusters. Importantly, our FDM-only friction model should be regarded as a conservative lower bound, since the inclusion of realistic FDM cores can only strengthen the survival of GCs through core stalling. This stalling mechanism not only preserves in situ populations that would otherwise be erased in CDM, but also strongly limits the mixing of in situ and ex situ clusters, yielding a bimodal radial distribution of GCs. Our results show that the demographics of GC systems encode a distinct dynamical signature of FDM in dwarfs. These predictions open a new pathway to constrain the boson mass parameter with upcoming Euclid DR1 observations of extragalactic GCs, while simultaneously offering a natural explanation for the long-standing Fornax timing problem.